During night driving in a motor vehicle, the reduced range of vision caused by the limited reach of the passing beam places heightened requirements on the driver. Because of the introduction of gas discharge headlights having greater light emission, in recent times, better illumination of the roadway has been achieved, compared to usual headlights. However, the visual range is even limited when using these new headlights, and therefore, to improve vision, it is planned to use night vision systems in motor vehicles.
Both passive and active night vision systems are known. Passive night vision systems are made up of a heat image camera. The disadvantage of night image systems is that it is difficult to produce images that are true to life, using a heat image camera. By contrast, active night vision systems are made up of an infrared emitting illumination unit, such as a halogen light having a filter, and one or more infrared-sensitive cameras. The illumination unit irradiates the vehicle's near field in the high beam region and the cameras photograph the reflected infrared high beam and reproduce the image on a monitor or a head-up display. In this context, headlights may be used for the visible passing beam and high beam to emit infrared light. However, the motor vehicle industry is increasingly planning proportionately to replace infrared-emitting halogen headlights with infrared-free xenon headlights. By their doing this, the use of additional infrared-emitting radiation sources becomes necessary. As the additional infrared-emitting radiation sources, the use of infrared-emitting lasers is possible, for example.
German Patent No. 42 43 200 describes a device for friend/foe identification of ground vehicles for military applications. In order to make visible occulted signatures for friend/foe identification, a heat image camera is linked to a CO2 laser. An observer emits a single light pulse and the infrared camera receives the reflected signal in synchronized fashion. A disadvantage of this device is that heat image cameras do not deliver true-to-life images. What is missing in German Patent No. 42 43 200 is any hint at a device or a method for generating images that are true to life and would be suitable for use in motor vehicles.